FIGURE 4.

Functional properties of gain-of-function hybrid mα6hβ3*-nAChR. A, representative traces are shown for inward currents in oocytes held at −70 mV, responding to application at the indicated concentrations of nicotine (shown with the duration of drug exposure as black bars above the traces), and expressing nAChR mα6^L9′S, mβ4 and hβ3 subunits. B, results for these and other studies averaged across experiments were used to produce concentration-response curves (ordinate, mean normalized current ± S.E.; abscissa, ligand concentration in log μm) for inward current responses to nicotine as indicated for oocytes expressing nAChR mα6 and mβ4 subunits alone (32 ×) or with hβ3 subunits (■) or expressing mα6^L9′S and mβ4 and hβ3 subunits (□), where current amplitudes are represented as a fraction of the peak inward current amplitude in response to the most efficacious concentration of nicotine. Much higher levels of evoked currents are evident for functional nAChR containing mα6^L9′S, hβ4, and hβ3 subunits when compared with receptors lacking hβ3 subunits. See Table 1 for parameters.